11 November 2002
chemicals may affect male fertility, MU researcher says
By LYNN FRANEY
living in agricultural mid-Missouri are markedly less fertile than
men living in New York, Minneapolis and Los Angeles, researchers
at the University of Missouri-Columbia have found.
researchers suspect that runoff from farm chemicals may be to blame.
results "are important to couples that are trying to conceive.
If we can find out what specific exposures were related to this
reduced semen quality, we might be able to prevent delays in conception
in the future," said Shanna Swan, the MU professor who led
said she hopes the study prompts further inquiry into how agricultural
chemicals negatively affect people's bodies.
study, conducted between 1999 and 2001, found that, on average,
fertile men in Columbia produced 58.7 million sperm per milliliter
of semen, compared with 80.8 million for men in Los Angeles, 98.6
million for men in Minneapolis and 102.9 million for men in New
another important measure, sperm mobility, fertile men in Columbia
also lagged behind their urban counterparts.
average, fertile men in Columbia produced just 113 million mobile
sperm per sample, compared with 162 million in New York, 196 million
in Los Angeles and 201 million in Minneapolis. Swan measured mobile
sperm by the sample, not by the milliliter, as was used to measure
the number of all sperm.
mobility measure is important because so few sperm make it to the
woman's fallopian tubes. After sperm has been deposited in the vagina,
only a small percentage find their way into the cervix and then
begin their journey though the uterus and into the fallopian tubes.
That journey must occur to fertilize the woman's egg. Only 1,000
or 2,000 sperm usually make it.
it's true that it only takes one sperm to conceive a pregnancy,
the length of time that it takes a couple to conceive is related
to the sperm quality -- how fast and directly the sperm swim, and
how they are shaped," Swan said. "If you follow couples
trying to become pregnant, those that have better semen quality
do conceive more quickly."
research corroborates an earlier study that found lower sperm counts
among men in Iowa City, Iowa, the only other semiagricultural region
used in a U.S. semen-quality study.
1974 study found the sperm concentration of Iowa City men was 48
million per milliliter of semen.
MU study will be published in today's edition of Environmental Health
Perspectives, the scientific journal of the National Institute of
Environmental Health Sciences. The unit of the National Institutes
of Health provided Swan a $2.8 million grant to conduct the research.
did not connect lower sperm counts and quality to particular agricultural
chemicals. But the study does highlight the significant difference
in land use among the other sites studied.
to the U.S. Department of Agriculture, Swan wrote, about 57 percent
of the land surrounding Boone County, where Columbia is located,
was used for agriculture, compared with 19 percent in Minneapolis,
5 percent in Los Angeles and 0 percent in New York.
study recruited 512 men whose pregnant partners were visiting hospitals
for prenatal care in Columbia and the three other cities.
noted where the men had lived before moving to Boone County, if
they were not Boone County natives. Swan said even very recent exposure
to farm chemicals, not just long-term exposure, could affect one's
who has been a professor at the MU School of Medicine for four years,
said she plans to publish a research article also based on the study's
data that deals with specific agricultural chemicals.
said she also would like to follow the children delivered by the
women whose partners participated in the study to see whether where
they were conceived -- an agricultural or urban area -- affected
their future health.
quality doesn't get affected in a vacuum," Swan said. "We
might call it the canary in the mine shaft. It indicates other potential
reproductive problems because it relates to testicular function.
There may also be problems in the woman's reproductive function.
And there may be indications in other health areas, perhaps links
to cancer down the line."